volcanic eruptions and other igneous activity
DESCRIPTION
Volcanic eruptions and other igneous activity. Viscosity – mobility of magma (resistance to flow) Factors affecting viscosity: temperature composition silica content dissolved gases. Factors affecting viscosity. Low gas content. High viscosity (low mobility). Low temp. High SiO 2. - PowerPoint PPT PresentationTRANSCRIPT
Volcanic eruptions and other igneous activity
Viscosity – mobility of magma (resistance to flow)
Factors affecting viscosity:
• temperature• composition
• silica content• dissolved gases
Factors affecting viscosity
Volcanic eruptions and other igneous activity
Low viscosity(high mobility)
High viscosity(low mobility)
High temp
Low temp
Low SiO2
High SiO2
Low gas content
High gas content
Importance of dissolved gases
Volcanic eruptions and other igneous activity
Low viscosity(high mobility)
High viscosity(low mobility)
Low violence eruption
High violence eruption
High pressure
Low gas content
High gas content
Low pressure
Materials extruded during an eruption
Volcanic eruptions and other igneous activity
• Lava flows• pahoehoe flows• aa flows• block lavas• pillow lavas
• Gases• Pyroclastic materials accdg to size
• ash and dust (welded tuff)• pea to walnut sized (lapilli, cinders)• blocks• bombs
• Pyroclastics accdg to texture• scoria (from basaltic magma)• pumice (from felsic magma)
Materials extruded during an eruption
Volcanic eruptions and other igneous activity
Lava flows – pahoehoe vs aa flows
Pahoehoe flows
Materials extruded during an eruption
Volcanic eruptions and other igneous activity
Lava flows – pahoehoe vs aa flows
aa flows
Materials extruded during an eruption
Volcanic eruptions and other igneous activity
Hardened pahoehoe flows = lava tubes
Materials extruded during an eruption
Volcanic eruptions and other igneous activity
Block lavas
Materials extruded during an eruption
Volcanic eruptions and other igneous activity
Pillow lavas
Materials extruded during an eruption
Volcanic eruptions and other igneous activity
Pillow lavas
The study of pillow lavas is important in reconstructing Earth’s geologic history. Can you tell why?
Materials extruded during an eruption
Volcanic eruptions and other igneous activity
Gases
Water vapor 70%CO2 15Nitrogen 5Sulfur dioxide 5
(low amounts of)ChlorineHydrogenArgon
Why is the study of volcanic gases very important?
Materials extruded during an eruption
Volcanic eruptions and other igneous activity
Gases
Materials extruded during an eruption
Volcanic eruptions and other igneous activity
Gases
Materials extruded during an eruption
Volcanic eruptions and other igneous activity
Pyroclastic materials – welded tuff
Materials extruded during an eruption
Volcanic eruptions and other igneous activity
Pyroclastic materials – welded tuff
Materials extruded during an eruption
Volcanic eruptions and other igneous activity
Pyroclastic materials – welded tuff
Materials extruded during an eruption
Volcanic eruptions and other igneous activity
Pyroclastic materials – welded tuff
Materials extruded during an eruption
Volcanic eruptions and other igneous activity
Pyroclastic materials – lapilli or cinders
From Vesuvius
Materials extruded during an eruption
Volcanic eruptions and other igneous activity
Pyroclastic materials – blocks
Materials extruded during an eruption
Volcanic eruptions and other igneous activity
Pyroclastic materials - bombs
Materials extruded during an eruption
Volcanic eruptions and other igneous activity
Pyroclastic materials (accdg to texture) - scoria
• Basaltic magma• Darker• Denser
Materials extruded during an eruption
Volcanic eruptions and other igneous activity
Pyroclastic materials (accdg to texture) - pumice
• Silica-rich magma• Lighter color• Less dense
Anatomy of a volcano
Volcanic eruptions and other igneous activity
Anatomy of a volcano - caldera
Volcanic eruptions and other igneous activity
Anatomy of a volcano - caldera
Volcanic eruptions and other igneous activity
Anatomy of a volcano - caldera
Volcanic eruptions and other igneous activity
Anatomy of a volcano – parasitic cones
Volcanic eruptions and other igneous activity
Anatomy of a volcano – fumaroles
Volcanic eruptions and other igneous activity
Volcano types – shield volcano
Volcanic eruptions and other igneous activity
• fluid basaltic lavas, often a few meters thick• broad, slightly domed structure• very few pyroclastic ejecta• lava tends to be more viscous as volcano matures
Volcano types – shield volcano
Volcanic eruptions and other igneous activity
Mauna Loa and Mauna Kea (upper white smudge) are 2 (of 5) overlapping shield volcanoes that make up Hawaii’s Big Island.
Volcano types – shield volcano
Volcanic eruptions and other igneous activity
Mauna Loa is over 9 km high (more than Everest’s 8.7km)
Volcano types – cinder cones
Volcanic eruptions and other igneous activity
• built from ejected lava fragments known as cinders or scoria• ash to walnut-sized ejecta
Volcano types – cinder cones
Volcanic eruptions and other igneous activity
• single eruptive episode = small cones• lava pipe is often immediately sealed with congealed lava• lava flows seldom happen; only at base, away from summit crater
Volcano types – composite cones
Volcanic eruptions and other igneous activity
• large, nearly symmetric structure of both lava and pyroclastic deposits• silica-rich magma travels only a short distance• gas-rich magma often produces violent eruptions
Volcano types – composite cones
Volcanic eruptions and other igneous activity
• steep summit with gently sloping flanks are due to lava flows• when young, lava tends to be more viscous, hence traveling farther to make a bigger base• mature volcanoes produce more viscous lava with increase the summit’s angle
Volcano types – hazards of composite cones
Volcanic eruptions and other igneous activity
sudden, often unexpected eruptions
Volcano types – hazards of composite cones
Volcanic eruptions and other igneous activity
Nuee ardente (glowing avalanches)
Volcano types – hazards of composite cones
Volcanic eruptions and other igneous activity
Lahar (mudflows of pyroclastic material)
Other volcanic landforms - Calderas
Volcanic eruptions and other igneous activity
Crater lake-type caldera
Other volcanic landforms - Calderas
Volcanic eruptions and other igneous activity
Hawaiian-type caldera
Other volcanic landforms - Calderas
Volcanic eruptions and other igneous activity
Yellowstone-type caldera
Other volcanic landforms – Fissure eruptions and basalt plateaus
Volcanic eruptions and other igneous activity
Fissure eruptions
Other volcanic landforms – Fissure eruptions and basalt plateaus
Volcanic eruptions and other igneous activity
Basalt plateaus
Other volcanic landforms – Lava dome
Volcanic eruptions and other igneous activity
Other volcanic landforms – Volcanic pipes
Volcanic eruptions and other igneous activity
Kimberlite diamond mines are volcanic pipes
Other volcanic landforms – Volcanic necks
Volcanic eruptions and other igneous activity
Volcanic necks are exposed pipes (erosion has long since removed the surrounding volcanic structure)
Intrusive igneous activity – plutons
Volcanic eruptions and other igneous activity
According to shape• Tabular• Massive
According to orientation• Discordant• Concordant
Dikes – tabular, discordantSills – tabular, concordantLaccoliths – tabular, concordantBatholiths
Other volcanic landforms – Dikes
Volcanic eruptions and other igneous activity
Other volcanic landforms – Sills
Volcanic eruptions and other igneous activity
Other volcanic landforms – Sills
Volcanic eruptions and other igneous activity
Other volcanic landforms – Sills
Volcanic eruptions and other igneous activity
Other volcanic landforms – Sills (columnar joints)
Volcanic eruptions and other igneous activity
Other volcanic landforms – Laccoliths
Volcanic eruptions and other igneous activity
Other volcanic landforms – Batholiths
Volcanic eruptions and other igneous activity
Other volcanic landforms – Batholiths (xenoliths)
Volcanic eruptions and other igneous activity
Other volcanic landforms – Stocks
Volcanic eruptions and other igneous activity
Stocks are smaller batholiths
Plate tectonics and igneous activity
Volcanic eruptions and other igneous activity
Igneous activity at convergent plate boundaries
Volcanic eruptions and other igneous activity
Volcanic island arcs
Igneous activity at convergent plate boundaries
Volcanic eruptions and other igneous activity
Igneous activity at convergent plate boundaries
Volcanic eruptions and other igneous activity
Continental volcanic arcs
Igneous activity at convergent plate boundaries
Volcanic eruptions and other igneous activity
Costa Rica coastal plains
Igneous activity at divergent plate boundaries
Volcanic eruptions and other igneous activity
Oceanic ridges
Igneous activity at divergent plate boundaries
Volcanic eruptions and other igneous activity
East African Rift
Intraplate igneous activity
Volcanic eruptions and other igneous activity
Mantle plume
Intraplate igneous activity
Volcanic eruptions and other igneous activity
Sahara desert volcanoes